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What is it? IO virtualization can come  in many flavors depending upon the exact problem you are trying to solve, but in general, it abstracts the association between the physical storage and the server (whether virtual or physical). This can be done at the block level (think products like EMC Invista, HDS Tagmastore, and IBM SVC) or at the file level (think Acopia or NetApp). Why is this important? Because virtual machines are taking over in IT shops. VMware started this craze and are the clear market leaders, while other hypervisors are coming on strong such as Xen and Virtuozzo. In order to get the most out of your virtual machines you need virtualized IO. When a virtual machine boots up it gets attached to a block device or a file device. When that migrates or fails over, it must take its data with it. Copying an entire file system is not practical so users look for ways to be able to get the LUN or the file to follow the virtual machine. This can be done with a networked or virtualized file system, but that has performance implications. Using a raw (block) device is better but the device must be logically split from the physical server so it can follow the virtual server. Still with me? This is where IO virtualization comes in. It provides the abstraction layer and allows the virtual machine data to follow the virtual server. Egenera has been doing this since day one. Our “servers” are really virtual servers that are built with physical blades, virtual networks, virtual consoles, and virtual IO devices. This is what enables our Processing Area Network to be so flexible. Add in a hypervisor like Xen or VMware, and it completes the picture, providing total flexibility. So, more and more use of server virtualization will undoubtedly drive more use of virtual IO. Be careful, though. Make sure you choose a solution that is fully integrated and works in unison with other virtualization technologies. Point products that only support part of the virtualization stack will be more problematic and cause more issues as you try to integrate all the parts together. I'd love to hear your thoughts on IO virtualization. You can contact me here by leaving a comment or reach me on e-mail at pmanca at egenera dot com.